Reactions of olefinic molecules in the presence of metal-containing catalysts to produce other olefinic molecules are known in the art as "disproportionation" reactions. The olefin disproportionation reaction can be visualized as the breaking of two existing double bonds between the first and second carbon atoms, and between the third and fourth carbon atoms, respectively, and the formation of two new double bonds, such as between the first and third carbon atoms and the second and fourth carbon atoms, respectively. A typical olefin disproportionation process is illustrated by U.S. Pat. No. 3,261,879, issued July 19, 1966, to Banks. wherein two similar non-symmetrical molecules of an olefin react in the presence of certain catalysts to produce one olefin of a higher carbon number and one olefin of a lower carbon number. For example, propylene disproportionates by the process of U.S. Pat. No. 3,261,879 to produce ethylene and butylenes.
A variation of this disproportionation process, which might be termed "reverse disproportionation" is illustrated by the Netherlands Patent No. 6514985 of British Petroleum Company Limited, published May 20, 1966, wherein, in one modification molecules of two dissimilar olefins are reacted to form two molecules of a single olefin product, e.g., ethylene and 2-butene react to form propylene.
Another variation of this process, being conveniently termed "ring opening disproportionation" to distinguish it from other variations, is disclosed by Netherlands Patent Application No. 6702703 of Phillips Petroleum Company, published Aug. 24, 1967, wherein a cyclic olefin and an acyclic olefin react to form a single product molecule. For example, ethylene reacts with cyclopentene by "ring opening disproportionation" to produce 1,6-heptadiene.
As used in this application, "disproportionation process" is meant to include all variations of disproportionations.
A variety of catalysts have been employed for conducting disproportionation reactions, such as those disclosed in U.S. Pat. No. 3,340,322, issued Sept. 5, 1967; U.S. Pat. No. 3,637,892, issued Jan. 25, 1972; U.S. Pat. No. 3,760,026, issued Sept. 18, 1973; U.S. Pat. No. 3,792,108, issued Feb. 12, 1974; U.S. Pat. No. 3,872,180, issued Mar. 18, 1975; and British Patent Specification No. 1,128,091, published Mar. 16, 1966. Among the catalysts that have been developed for disproportionation include inorganic refractory materials containing molybdenum and/or tungsten oxide.
Several patents disclose the use of promoter to enhance the disproportionation catalyst activity. Elemental metal promoters selected from the group consisting of barium, magnesium, tungsten, silicon, antimony, zinc, manganese and tin are disclosed in U.S. Pat. No. 4,568,788, issued Feb. 4, 1986, U.S. Pat. No. 4,522,936, issued June 11, 1985, U.S. Pat. No. 4,524,235, issued June 18, 1985 and U.S. Pat. No. 4,629,719, issued Dec. 16, 1986. In addition, organometallic compounds, such as aluminum and tin alkyls to promote solid catalysts including molybdenum and rhenium oxide for the disproportionation are disclosed in U.S. Pat. No. 4,454,368, issued June 12, 1984 and U.S. Pat. No. 3,829,523, issued Aug. 13, 1974.
It is an object of this invention to provide a catalyst system with novel promoters for olefin disproportionation at high activity. Another object is to provide a catalyst system adapted for high efficiency reaction and high selectivity to alpha olefin production from internal olefins and ethylene. The catalyst system is required to produce alpha olefins without significant olefin isomerization and ethylene polymerizations. It is a further object of this invention to maintain the improved results of the novel promoters of this catalyst system when used with a cyclic olefin reactant which is more reactive than a non-cyclic olefin and thus has a tendency to polymerize and an ethylene or propylene reactant to produce 1,6-heptadiene and 1,6-octadiene, which are useful chemical intermediates. Simply stated, the catalyst system may be used in the presence of a novel promoter and give desired cross-metathesis products from ethylene without side reactions.
An additional advantage is evidenced by the fact that reactions can be carried out at ambient temperature during the process, and the process requires no additional heat or energy activation sources.
The alpha olefin production from internal olefins and ethylene (i.e., ethenolysis) was reported by using Re.sub.2 O.sub.7 -on-alumina catalyst at 140.degree. C. in U.S. Pat. No. 3,647,906, issued Mar. 7, 1972. However, the purities or selectivities to alpha olefins were not reported. In U.S. Pat. No. 3,658,927, issued Apr. 25, 1972 and Journal of Catalysis, 7, 269-276 (1967), a heterogeneous molybdenum oxide catalyst at high temperature was used for ethenolysis. The reaction produced alpha olefin with either low conversion or low selectivity.
Dienes prepared from cyclic olefins and ethylene using rhenium, molybdenum and tungsten catalysts are disclosed in U.S. Pat. No. 3,878,262, issued Apr. 15, 1975, U.S. Pat. No. 3,424,811, issued Jan. 28, 1969, and U.S. Pat. No. 3,792,102, issued Feb. 12, 1974. However, the use of molybdenum oxide catalysts to prepare dienes at high yield at room temperature is not disclosed. For example, in U.S. Pat. No. 3,981,940, issued Sept. 21, 1976, the synthesis of 1,9-decadiene from cyclooctene and ethylene using molybdenum oxide catalyst promoted by organoaluminum compound gave only 8% conversion at room temperature.
The present invention is therefore directed to a method of improving the activity of a disproportionation catalyst for converting olefins into olefins having different numbers of carbon atoms than the feed olefinic hydrocarbons, particularly to a method of improving the yield of alpha olefins and dienes prepared from ethylene reactions.